Bob/ and others In the 15 I am building I moved the drive axle forward and added an air ride Tag axle. I would like to be able to release the air from the tag and add air the the air bags that I will but on the drive axle when I make shape turns in tight places. The Tag is already set up to be lifted. I see on another board you talked about drawings from Prevost that do just that. If you have time and want to could you please get me that drawing ? I think I could figure it out but why reinvent the wheel.

Up in the articles section on the prevostcommunity board go down apiece and there are two different articles on the level low system. Both will include the tag lift feature. The non video one is simple with drawing only. Basic will disable your tag brakes when lifted. Can be done with series 200 norgren valves (that would include lifting). If not go to prevostcar web site. Go down to tech publications where they have pneumatic and pull up diagram for my coach. (W-6553) Just pay attention to tag lift function. If this doesn't work I'll try to get one of the kids to get you the info sent to you on the computer ----I'm challenged for sure. I think Jon put a direct link to prevost up below my post. Just plug my #'s in and it will show how they cut service brake signal to tag and lift requires extra r-12 if memory serves me correct. Mine or antilock so might have a couple extra valves if you aren't running antilock. Hope this is clear as mud but the drawings help. Bob PS see what you can find then we will go from there.

Basic all it does is take the tags out of level system and disables brakes. If your only concerned when turning I wouldn't worry about brakes. If you want to load drives in case of snow or mud you need to disable brakes on tags. Your choice. Bob

Excuse me if I am hyjacking this thread. The only time I have ever dumped the tag (does't lift, just dumps) is when I got stuck in wet grass. I have a gravel driveway and to turn around behind my house, I have to pull forward and back a couple times with the steering at full cut. With only 212 inches between the steer and drive axles, the old WL will turn quite short and with near 19k on the drive and 7k on the tag, I can't see how it would turn much shorter with the tag dumped. Also, it doesn't chew the gravel and grass up very bad at all.

I do not know if the tag brakes work when dumped. I sit around and think of this stuff, but can never remember to experiment to find out when in the bus. If the tag brakes do work when dumped, I think it would tear the grass and gravel up.

Bob I got the article from Prevost community site. I will read them and let you know if that is what I need. I don't think I will mess with the brakes. Thank You for your help.

Low Class I am running 4 super singles on the rear of my Eagle and think it will be less wear and tear on things when turning in tight places. You can do what you want but if I had the ability to lift the tag I would for the above reason.

Unless you can use absolutely the last inch of your coach's turning radius; that your driving skills do not waste any space on corners, lifting the tag is a myth.

In order to test, in a big parking lot, lift the tag, set the coach up in full lock, once it is in full turn, get out and put down a marker at the drive wheels, then do a complete circle, stopping on the opposite side to lay down a 2nd marker, and on completion, the drives should come back to the first marker.

Drop the tags and repeat, and see how far out from the tighter circle the coach ends up.

On a corner, which would be 1/4 of the circle you just completed, that's all you buy if your skills are good enough to take advantage of that small potential.

In fooling with a 45 foot H3 45 back a bunch of years ago, there was somewhat less than 4 feet tighter turning circle across the diameter, so less than a foot at a corner, if you can gauge it right.

It's difficult for me to see the reasons for raising the tag axles on a bus as mythical - no matter the length. Here's the way I see it.

If the forward axle is the drive unit and has the most downforce of the two axles, then the tag is going to 'drag' and scuff the tires as it unsuccessfully attempts to follow the tighter radius of the drive axle.

With that said, now set the scene where the tag is ahead of the drive unit but lighter in downforce or, what if the the weight distribution is reversed? What if in the first scene the tag is heavier than the driver?

My contention is that you cannot turn two wheels, which are ilocked in tandem, within the same radius. Therefore, the tires of one axle are bound to skid - with weight distribution between the two axles being a significant factor.

Assuming, in the first scene above, the drive axle is dominant, damage will be incurred upon the tag unit tire fom skidding. Lifting the tag axle tire from the road surface will not only remove that potential for damage but, will also relieve pressure on both the engine and driveline - not to mention the road surface.

My thinking leads me to believe those are the reasons major bus manufacturers install lifting tag axles - especially on the 45 footers. The longer and heavier the vehicle, the greater the damage incurred.

I'd wager a good cold Coors that those are the same reasons Wayne is using in considering a tag-lift-axle in his big Eagle project!

I have actually had this in the back of my mind since we started talking. Lot of surface area there on tag for braking and side twisting. How many times have we had dead axle hung up on gravel? Would have been nice to unload it. Guess I'm the only fool that ever owned a tandem with a dead axle. Everyone needs to follow Rusty"s Build ..One of the best. Basic when tag lift is on there is a valve turned on that kills service brake to tags. Requires a separate R-14 for tag and Norgren valve to interrupt signal to service brake to tag. Rusty ; thanks for helping out on my hydraulic clutch set up. Bob

The point of rotation, if you will, is somewhere between the drive and the tag. As noted, the position of this ghost point is dependent on weight distribution and the immediate traction under each tire during the turning movement.

All the tires scrub, it's a matter of which ones scrub the most.

The 45 foot coaches are putting far more weight on the tags than the 40 foot coaches, both in pounds, and in percentage of the total load back there. Easily witnessed with their propensity to spin the drives in slippery conditions in ways a 40 foot coach never did.

Unloading or lifting the tags has to do primarily with traction for the drives, and periodically avoiding ripping the asphalt off a fresh parking lot in the summer sun.

Oh, and swinging your tail out a shade more so you can whack something on the off side, where you weren't looking.